Dangerous condition at best.
Buy an inductive clamp on timing light and clamp it to the distributor COIL wire (not spark plug wire) and arrange the light so its visible while driving. If the light is intermittient or goes out, then look at the ignition system.
If its a loss of fuel, the timing light will continue to work as long as the engine is rotating on the transmission torque.
Look in the exhaust pipe for signs of excess fuel (black deposits).
Install a fuel pressure gauge to monitor the pressure whhile driving. i realize that ones not as easy as a clamp on light, but its easier than picking up motorhome pieces in the freeway after a semi runs over it...
Like swampdog wrote, those ignition modules can be a real pain, good to replace from time to time and ALSo make sure the connectors are TIGHT on the terminals. I replace / solder them on. AND make sure there is heat sink compound on the heat sink pad, that unit runs very warm.
if you cant find the stalling problem I can build a computerized data collection unit thats suitable to connect to the hostile electrics under the hood and can be read out on a PC while driving. I built one for a propane vehicle project. Neat unit, it captures and records the electrical signals on a PC so they can be played back. I arranged it to capture FI signals, fuel pressure, oxygen sensor but it has up to 8 inputs.
Also, since its GM related, the in-tank fuel pumps can do that also, the old manual pumps just tended to quit outright.